When upgrading or modifying the operation of an application server associated with a database management system (DBMS), it is usually desired to have little or no downtime during the upgrade or modification. Therefore, changes to the schema of the database need to be backward compatible, in the sense that existing application code can still properly address the DBMS until a new application code is fully deployed.
In such migration model, changes of adding new tables and columns are acceptable while altering or deleting columns and tables are forbidden. If these rules are not adhered to, the application server may suddenly, during migration, fail to address the database.
When the schema contains a tree (“hierarchical”) model (often defined as nodes having a parent-child relationship), as common in relational database management systems (RDBMSs), such migration becomes challenging—especially when a new node has to be inserted in an intermediate location in the hierarchy.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the figures.